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fpu_int.c revision 1.10 
      1 /*	$NetBSD: fpu_int.c,v 1.10 2011/07/18 14:11:27 isaki Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1995 Ken Nakata
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  *
     16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
     17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     19  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     26  * SUCH DAMAGE.
     27  *
     28  *	@(#)fpu_int.c
     29  */
     30 
     31 #include <sys/cdefs.h>
     32 __KERNEL_RCSID(0, "$NetBSD: fpu_int.c,v 1.10 2011/07/18 14:11:27 isaki Exp $");
     33 
     34 #include <sys/types.h>
     35 
     36 #include <machine/reg.h>
     37 
     38 #include "fpu_arith.h"
     39 #include "fpu_emulate.h"
     40 
     41 /* FINTRZ - always round to zero */
     42 struct fpn *
     43 fpu_intrz(struct fpemu *fe)
     44 {
     45 	register struct fpn *x = &fe->fe_f2;
     46 	register int sh, clr, mask, i;
     47 
     48 	/* special cases first */
     49 	if (x->fp_class != FPC_NUM) {
     50 		return x;
     51 	}
     52 	/* when |x| < 1.0 */
     53 	if (x->fp_exp < 0) {
     54 		x->fp_class = FPC_ZERO;
     55 		x->fp_mant[0] = x->fp_mant[1] = x->fp_mant[2] = 0;
     56 		return x;
     57 	}
     58 
     59 	/* real work */
     60 	sh = FP_NMANT - 1 - x->fp_exp;
     61 	if (sh <= 0) {
     62 		return x;
     63 	}
     64 
     65 	clr = 2 - sh / 32;
     66 	mask = (0xffffffff << (sh % 32));
     67 
     68 	for (i = 2; i > clr; i--) {
     69 		x->fp_mant[i] = 0;
     70 	}
     71 	x->fp_mant[i] &= mask;
     72 
     73 	return x;
     74 }
     75 
     76 /* FINT */
     77 struct fpn *
     78 fpu_int(struct fpemu *fe)
     79 {
     80 	register struct fpn *x = &fe->fe_f2;
     81 	register int rsh, lsh, wsh, i;
     82 
     83 	/* special cases first */
     84 	if (x->fp_class != FPC_NUM) {
     85 		return x;
     86 	}
     87 	/*
     88 	 * even if we have exponent == -1, we still have possiblity
     89 	 * that the result >= 1.0 when mantissa ~= 1.0 and rounded up
     90 	 */
     91 	if (x->fp_exp < -1) {
     92 		x->fp_class = FPC_ZERO;
     93 		x->fp_mant[0] = x->fp_mant[1] = x->fp_mant[2] = 0;
     94 		return x;
     95 	}
     96 
     97 	/* real work */
     98 	rsh = FP_NMANT - 1 - x->fp_exp;
     99 	if (rsh - FP_NG <= 0) {
    100 		return x;
    101 	}
    102 
    103 	fpu_shr(x, rsh - FP_NG);	/* shift to the right */
    104 
    105 	if (fpu_round(fe, x) == 1 /* rounded up */ &&
    106 	    x->fp_mant[2 - (FP_NMANT-rsh)/32] & (1 << ((FP_NMANT-rsh)%32))
    107 	    /* x >= 2.0 */) {
    108 		rsh--;			/* reduce shift count by 1 */
    109 		x->fp_exp++;		/* adjust exponent */
    110 	}
    111 
    112 	/* shift it back to the left */
    113 	wsh = rsh / 32;
    114 	lsh = rsh % 32;
    115 	rsh = 32 - lsh;
    116 	for (i = 0; i + wsh < 2; i++) {
    117 		x->fp_mant[i] = (x->fp_mant[i+wsh] << lsh) |
    118 		    (x->fp_mant[i+wsh+1] >> rsh);
    119 	}
    120 	x->fp_mant[i] = (x->fp_mant[i+wsh] << lsh);
    121 	i++;
    122 	for (; i < 3; i++) {
    123 		x->fp_mant[i] = 0;
    124 	}
    125 
    126 	return x;
    127 }
    128